I see one problem you are going to have with the way you are going about it. You don't have a way to stop the forward and back stroke length. So what is going to happen is the bolt will either smash into the body or the pin will smack the end of the slot going back unless you adjust the pump handle to hit the body and bottom out before it goes back too far. On the front stroke your your bolt tip will either hit crown of barrel or the bolt pin will smash into the slot that is milled.
I made my pump carrier out of delrin and made it quite a bit smaller then the bore so it won't drag. The pump arm I made out of stainless steel that is polished and I made a a delrin sleeve that the stainless steel rod fits inside of there is zero flex on the pump arm and no metal to metal contact. On my pump guide I made it look the one you made on the valve side (so I have two long pump guides, one a volumizer and other hollow) but bored it out so the pump arm and internals are completely sealed from dirt or paint.With the delrin insert tube I can adjust the length on my forward stoke and I have a urathane autococker bumper from wgp cocking rod between my delrin hammer and delrin guide tube so it does not clank on forward stroke and the back stroke I was able to adjust with the length of the pump guide that goes into the actual pump arm. I came up with the idea and built it about 2 and a quarter years ago. I have played with it 18 days and have had zero problems or any signs of wear. Your pump arm is going to eat up the pump guide cap you made and will get sloppy. Might want to think about making a third guide, since your design only really has one guide and one pump arm that will take flex. Let me know if you have any questions. You had PM'd me on MCB a year or so ago and we talked about this. Looking good so far.

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"Even now in Heaven there are Angels carrying savage weapons."
"Did you ever notice how in the Bible, when ever God needed to punish someone, or make an example, or whenever God needed a killing, he sent an angel?"BALLERS INC DESTROYED MY ANGEL

heat might be your friend too. the body is aluminum so it should expand more than the steel pins if heat is applied. Might be just enough.

__________________
"Even now in Heaven there are Angels carrying savage weapons."
"Did you ever notice how in the Bible, when ever God needed to punish someone, or make an example, or whenever God needed a killing, he sent an angel?"BALLERS INC DESTROYED MY ANGEL